Angle of incidence restriction for optical filters

Abstract

A filter may include a first component filter associated with a first angle shift and a first passband. The filter may include a second component filter associated with a second angle shift and a second passband, wherein the first angle shift, the first passband, the second angle shift, and the second passband are configured to make the filter transmissive to a spectral range of light at a first angle of incidence and reflective to the spectral range of light at a second angle of incidence.

What is claimed is: 
     
       1. A composite optical filter, comprising:
 a substrate; 
 a first component optical filter disposed onto the substrate,
 wherein the first component optical filter is associated with a first angle shift, 
 wherein the first component optical filter is a low angle shift passband filter manufactured using hydrogenated silicon (Si:H), 
 wherein the low angle shift passband filter is associated with less than 20% angle shift at a particular range of angles of incidence, and 
 wherein the particular range of angles of incidence is a range of approximately 0 degrees to approximately 60 degrees; and 
 
 a second component optical filter disposed onto the first component optical filter,
 wherein the second component optical filter is associated with a second angle shift that is different from the first angle shift, and 
 wherein the composite optical filter is configured to be transmissive to light at a first range of angles of incidence and is configured to block light at a second range of angles of incidence that is different from the first range of angles of incidence. 
 
 
     
     
       2. The composite optical filter of  claim 1 , wherein the first range of angles of incidence is between approximately 0 degrees and approximately 30 degrees. 
     
     
       3. The composite optical filter of  claim 1 , wherein the first range of angles of incidence is between approximately 0 degrees and approximately 45 degrees. 
     
     
       4. The composite optical filter of  claim 1 , wherein the second range of angles of incidence is greater than approximately 30 degrees. 
     
     
       5. The composite optical filter of  claim 1 , wherein the second range of angles of incidence is greater than approximately 45 degrees. 
     
     
       6. The composite optical filter of  claim 1 , wherein the second range of angles of incidence is between approximately 0 degrees and approximately 30 degrees and wherein the first range of angles of incidence is greater than approximately 30 degrees. 
     
     
       7. The composite optical filter of  claim 1 , wherein the composite optical filter is transmissive to greater than a threshold percentage of light at the first range of angles of incidence, and
 wherein the threshold percentage is at least one of:
 approximately 75%, 
 approximately 90%, 
 approximately 95%, 
 approximately 99%, 
 approximately 99.9%, 
 approximately 99.99%, or 
 approximately 99.999%. 
 
 
     
     
       8. The composite optical filter of  claim 1 , wherein the composite optical filter is configured to block a threshold percentage of light at the second range of angles of incidence, and
 wherein the threshold percentage is at least one of:
 approximately 75%, 
 approximately 90%, 
 approximately 95%, 
 approximately 99%, 
 approximately 99.9%, 
 approximately 99.99%, or 
 approximately 99.999%. 
 
 
     
     
       9. The composite optical filter of  claim 1 , wherein the composite optical filter is configured to be transmissive to light at a particular spectral range at the first range of angles of incidence and is configured to block light at the particular spectral range at the second range of angles of incidence. 
     
     
       10. The composite optical filter of  claim 9 , wherein the particular spectral range is between at least one of:
 approximately 600 nanometers (nm) and approximately 1200 nm, 
 approximately 700 nm and approximately 1100 nm, or 
 approximately 800 nm and approximately 1000 nm. 
 
     
     
       11. The composite optical filter of  claim 9 , wherein the particular spectral range is between at least one of:
 approximately 1200 nanometers (nm) and approximately 2000 nm, 
 approximately 1400 nm and approximately 1800 nm, or 
 approximately 1500 nm and approximately 1700 nm. 
 
     
     
       12. The composite optical filter of  claim 9 , wherein the particular spectral range is between at least one of:
 approximately 200 nanometers (nm) and approximately 4000 nm, 
 approximately 1000 nm and approximately 3000 nm, or 
 approximately 1500 nm and approximately 2500 nm. 
 
     
     
       13. An optical system, comprising:
 an optical filter including a plurality of component optical filters configured to filter an input optical signal and provide a filtered input optical signal,
 wherein the plurality of component optical filters is configured to block a first portion of the input optical signal that does not satisfy an angle of incidence threshold and to pass a second portion of the input optical signal that does satisfy the angle of incidence threshold, 
 wherein the plurality of component optical filters include a low angle shift filter manufactured using hydrogenated silicon (Si:H), 
 wherein the low angle shift filter is associated with less than 20% angle shift at a particular range of angles of incidence, and 
 wherein the particular range of angles of incidence is a range of approximately 0 degrees to approximately 60 degrees; and 
 
 an optical sensor configured to receive the filtered input optical signal and provide an output electrical signal. 
 
     
     
       14. The optical system of  claim 13 , wherein a maximum transmissivity of the optical filter is at a lesser angle of incidence than a minimum transmissivity of the optical filter. 
     
     
       15. The optical system of  claim 13 , wherein the low angle shift filter is a long wave pass (LWP) optical filter. 
     
     
       16. The optical system of  claim 13 , wherein the plurality of component optical filters further include a short wave pass (SWP) optical filter. 
     
     
       17. A filter, comprising:
 a first component filter associated with a first angle shift and a first passband,
 wherein the first component filter is a low angle shift filter manufactured using hydrogenated silicon (Si:H), 
 wherein the low angle shift filter is associated with less than 20% angle shift at a particular range of angles of incidence, and 
 wherein the particular range of angles of incidence is a range of approximately 0 degrees to approximately 60 degrees; and 
 
 a second component filter associated with a second angle shift and a second passband,
 wherein the first angle shift, the first passband, the second angle shift, and the second passband are configured to make the filter transmissive to a spectral range of light at a first angle of incidence and reflective to the spectral range of light at a second angle of incidence. 
 
 
     
     
       18. The filter of  claim 17 , wherein the first angle of incidence is less than approximately 30 degrees and the second angle of incidence is greater than or equal to approximately 30 degrees. 
     
     
       19. The filter of  claim 17 , wherein at least one layer of the second component filter is a tantalum pentoxide (Ta 2 O 5 ) material. 
     
     
       20. The filter of  claim 17 , wherein the filter is a collimator.